1. Field of the Invention
The present invention relates to a control device for an electric blanket.
2. Description of the Related Art
A typical electric blanket includes at least one heating element that generates heat energy for keeping the user's body warm. The electric blanket is electrically connected to an AC power source and includes a switch for activating the heating element. As illustrated in FIG. 4, the voltage and current from the AC power source are sine functions of time. Namely, the voltage of an AC power source of 60 Hz changes sixty (60) times per second as sine waves T1 having peak voltages at points a2 and a4. As illustrated in FIG. 5, when the switch is turned on, after a period of time “b” (i.e., on-time) corresponding to the peak voltage a2 has passed, the voltage applied to the heating element is suddenly increased from 0 to a2, resulting in noise signals and electromagnetic waves that are harmful to the user's body. Since the on-time of the electric blanket cannot be precisely controlled, the electromagnetic waves resulting from momentary voltage change would be a problem after a long-term use of the electric blanket.